Electric switch



Dec. 16, 1941- R. A. MACDONALD ELECTRIC SWITCH Filed March 31, 1939 2 SfieetsSheet l Dec. 16, 1941. R. D NALD 2,266,468

ELECTRIC SWITCH Filed March 31, 1939 2 Sheets-Sheet 2 ,4 4% 52-2 3} L l Jig; 497

Patented Dec. 16, 1941 UNITED STATES PATENT OFFICE ELECTRIC SWITCH Roderick Alan Macdonald, Richmond, Va.

Application March 31, 1939, Serial No. 265,301

8 Claims.

The present invention relates to manually operable electric switches of the type having thermostatic timing controls. More particularly, my invention is concerned primarily with a device of this type associated with a lamp socket and designed in one of its positions to break the circuit through the lamp after a predetermined period.

Preferably, the parts of the switch and control mechanism are so designed and assembled that they may be incorporated readily within the usual two-piece external housing of a conventional pu1l-chain lamp socket; but it will be apparent as this discussion proceeds that the invention may be embodied in other forms of lamp sockets, and, in fact, in switches that are more or less remote from the lamp or other unit that is to be controlled.

It is the primary object of the present invention to devise an improved switch of this general character that is compact, sturdy, positive and reliable in operation, and yet that can be placed on the market for sale at low cost. An object is to provide a lamp socket switch with a thermostat control in such manner that the lamp does not become dimmed when a circuit is completed through the control unit. Another important object of my invention is to provide a lamp socket in which one or more of the switch elements are adjustable for obtaining and maintaining accuracy of relationship between movable parts. A further object is to so design the switch mechanism that the electrical connections for the wire terminals can be made conveniently.

Still another object of this invention resides in the provision of an upright thermostat unit that requires but a small part of the space above the switch-supporting block.

It is also an object to make the thermostat unit readily replaceable and, in fact, to devise a standard switch assembly that may be made for conventional use without thermostatic control but to which a control unit may be added readily at the factory or by the ultimate purchaser.

It is a further object of my invention to provide an improved switch mechanism per se, in which no pawl and ratchet mechanism is required, the manually actuated contact element being simply oscillatable to and fro.

The foregoing and other objects will clearly appear from a study of the following detailed description when taken in conjunction with the accompanying drawings and the appended claims.

In the drawings:

Fig. 1 is a perspective view of a preferred form of my improved switch and control mechanism as mounted upon a block for incorporation in a conventional internally insulated two-piece lamp socket shell;

Fig. 2 is a top plan view of the device of Fig. 1, with the movable contact element in another position;

Fig. 3 is a sectional view taken vertically substantially along the line 3-3 of Fig. 2;

Fig. 4 is a detail view of the oscillating unit of Figs. 1-3;

Fig. 5 is an enlarged detail View of an element of the oscillating unit;

Fig. 6 is a diagrammatic representation of the several circuit making and breaking elements, and depicts the positions or path of travel of the oscillating contact element as it goes through a complete cycle; and

Fig. '7 is a detail view of the fixed contact element.

In the drawings, wherein like characters are employed to designate like parts and wherein the two-part housing shell has been omitted for clarity and because its structure has become so well known, there is shown a switch and control mechanism mounted upon a cylindrical block I0 that carries a conventional copper socket ll designed to receive the screw-shaped end of an electric lamp in the usual manner. The block must be an electrical insulator and may be formed of vitreous substance, a molded resin, or other suitable material. It has several special apertures and recesses that may be formed by molding, cutting or other operations, depending upon the chosen material of which it is made.

The socket II is attached to the bottom of the block by fastening elements, one of which consists of a conducting screw ll! of brass or the like that has its upper threaded end extending through a plate portion l3 of a contact assembly C which will be described in detail later. A pair of nuts l4 assist in anchoring the plate upon the block, the anchorage being completed by a screw [5. The plate I3 thus is in circuit with one end of the lamp filament when the lamp is screwed into the socket. The other side of the lamp filament is conventionally connected centrally of the socket II to an elongated conducting unit [6 that passes through the center of the block and includes a screw I! for attaching the terminal of a lead wire [8 to its upper end. The socket is transversely slotted conventionally at to avoid contact with the lower end of the unit IS.

The other lead wire 2! is brought like the lead l8 into the housing (not shown) in the usual way through a central aperture in the cap por-' tion of the latter, and has its terminal connected to a metal post 22 by means of a pair of nuts 23 threaded onto the upper end of said post. Between its ends the post is provided with an integral collar 24 that is drawn firmly against the block by a screw 25 that engages the lower end of the post and the bottom of a recess 26 formed in the block IE3. Provision of the recess assures absence of electrical contact between the post and the screw 25 and the socket H.

The collar 24 has a hole, as shown, for reception of one end of a light coil spring 27 that surrounds the post, the other end of the spring extending into a hole 28 formed in a fibrous disc or plate 38. This disc snugly receives a metal conducting bushing 35 that is freely rotatable on a smooth cylindrical portion of the post. The bushing and the disc are rigidly united by a contact arm 32 that is riveted to the dis at 33 and locked at one square end to the bushing by means of a cross-cut slot 34 in the surface of the bushing. In this manner, the arm 32 is brought into electrical contact with the bushing while simultaneously holding the latter against rotation independently of the fibrous disc.

The spring 21' is under slight axial compression, and under sufiicient torsion to tend to carry the arm 32 to its full line position of Fig. 2, where it may be in contact with a stop or with the insulating shell that conventionally lines the surrounding housing (not shown). The disc has a peripheral groove, as shown, for reception of a conventional pull-chain 35 that has one end anchored to the disc and its other end designed to be pulled manually to oscillate the disc against the spring resistance. A conducting washer 35 (Fig. 3), is provided between the nuts 23 and the bushing 3!.

The contact arm 32 has vertical spring or flexibility, and is of sufficient length to swing into circuit making and breaking cooperation with the upper structure of the contact assembly C. It will be perceived that when arm 32 contacts any part of this structure, a circuit will be established through lead 21, arm 32, assembly C, the socket l l, the lamp filament, the unit l5 and the lead IS; and that when such contact is eliminated the circuit is broken. The free end of the arm 32 is twisted about its axis as shown, for a purpose that will appear from the following description of the contact assembly C.

Above its anchoring plate 53, the assembly C comprises an integral upright wall 3? which in turn carries an integral horizontal platform 38 at about the level of the axis of the arm 32. The forward end of this platform is bent backwardly upon itself to form a cam 48 and a wedge-shaped pocket 4! (see also Fig. 7). To the rear of the cam #38. the platform is laterally slotted at 52 and bent on a transverse line to form a vertical upright wall 43. Preferably all of these parts are in one piece and the final shape is obtained by bending operations.

Secured to the wall 31, as by spot Welding at id,

is the vertical wall 45 of an added guiding and abutment element comprising an integral sloping platform 36 and an integral vertical wall i! that is parallel to the wall '13. For reasons about to appear, it is essential that the gap between parts 40 and be less than the width of the free end of the arm 32, and that the length of the slot 42 be greater than the width of said free end.

When the chain 35 is pulled to oscillate the arm 32 counterclockwise, the leading or upturned edge of the outer end of the arm engages the lower part of cam 40 and causes the arm to deflect upwardly as it rides over the cam. The arm end drops onto the sloping platform $6 after over-riding the cam, and then is stopped by the abutment wall 47. The attendant or operator then releases the chain to permit the spring 21 to oscillate the arm 32 clockwise, and the arm end due to its shape and deflectionthen rides off the platform 46 and into the trapping pocket 4|, where it will remain to maintain a lighting circuit until the chain is pulled again.

To turn off the light, the operator gives the chain a second pull, causing the arm end to move rearwardly against the vertical stop wall 43. In doing this, it passes the slot 42, which permits the arm end to drop slightly to its natural position or initial level, so that its trailing edge now is lower than the platform 38. 'Therefore, when the chain is released the arm will avoid the pocket M and travel below the latter and the platform 38, thus permitting the spring Z'l to return the arm 32 toward its initial broken-circuit position. In the preferred and illustrated arrangement, however, automatic means is interposed in the path of the swinging arm to hold it from complete return for a predetermined time interval so that the lamp will not immediately be cut out of the circuit. This means comprises a thermostat constructed and arranged as follows.

A notch 50 is out or otherwise formed in the block 10 so that the arm 32 must swing over the notch in passing to its on and 01f positions. A thermostat unit, in the form of an elongated bimetalli element 5! wrapped with a coil of resistance wire 52, is disposed in upright position against one wall of the notch within a rectangular recess 53 by means of a nut 54 that is received by the threaded end of a screw 55. The screw extends through a portion of the block and has its head disposed within a block recess 56. One end of the coil 52, which is covered with heat-resistant insulation, is secured in contact with the bimetallic element, and its other end is connected to the center terminal it of the lamp socket by the screw ll. Therefore, when the arm 32 engages both the assembly C and the element 5! (as in Fig. 1-) the coil 52 is energized toheat the element 5!, thereby causing the latter to bend away from the supporting wall at its upper end into the broken line position shown in Fig. 2.

The coil 52 may comprise bare wire surrounding an asbestos sheath enclosing the bimetallic element 5|, and it is understood that any suitable or equivalent arrangement may be provided. Preferably the arm 32 remains in contact with the cam assembly C when its trailing edge engages the bimetallic element, and the coil 52 is wired in parallel with the lamp, so that the current for lamp illumination does not pass through the coil. Therefore, the lamp is not dimmed during the heating period. By notching the block to receive the bimetallic element and by securing the later to the block adjacent its lower end, vertical compactness of the device is assured without detracting from the deflection range of the upper end of said element. In other words, a desirably long element is utilized which readily flexes into its broken line position, when heated, to release the contact arm 32 and permit said arm to return to its initial position.

The operation of the described mechanism now should be fairly obvious, but it may be helpful to summarize it with reference to the diagrammatic view of Fig. 6, wherein the curved end of arm 32 is shown in siX important positions. From its initial open circuit position 32l the contact arm clears or rides over the element 55 and reaches the position 32-2 where its upper or leading edge strikes the cam surface 46. It slides over the surface it and rides on the pla form 45 into engagement with the stop il, position 32-3. It has been deflected upwardly and accordingly, upon its return movement, it snaps into the pocket ll, position where it will remain to keep the circuit closed indefinitel until the operating chain is pulled again.

The second pull on the chain throws the arm end into position and when the chain is released said end moves to position 32Ei, its lower edge clearing the platform 38 and its upper edge being in yielding contact with the platform. The lower edge also engages the element 5! with insufficient force to thrust the latter out of the way. However, a circuit through the shunted coil 52 now has been completed so that after a predetermined interval the latter has heated the element 5| sufiiciently to cause it to flex and permit the arm end to return to its initial position 32-l.

It will be perceived that accuracy of relationship of the arm 32 to the other contacts may be obtained and maintained by varying the height of the bushing 3|, which is freely slidable on its supporting post. This adjustment is effected by turning the nuts 23 a slight amount in the proper direction.

It is to be understood that the invention is not limited to the particular construction herein shown and described as various changes that may be made in the design, shape and relative arrangement of the parts fall within the spirit of my invention as set forth in the following claims.

I claim:

1. A lamp socket switch comprising a substantially cylindrical insulating block carrying a conventional lamp socket at one of its ends, an oscillating element arranged at the other end on an axis substantially parallel to that of the block, said element carrying a contact member that is connected to one side of a power line, a contact contact with one end of the lamp filament, means yieldingly biasing said oscillating element to carry said contact member away from the contact assembly, and manually operable means for swinging said element to bring said contact member towards and into cooperation with said contact assembly, said assembly including means for trapping and holding said contact member on every alternate swing of said oscillating element against the resistance of said biasing means.

2. In the switch defined in claim 1, automatic timing means disposed below the path or said contact member in moving from the initial position thereof to said assembly, said switch assembly including means to depress said contact member into engagement with said automatic timing means as said contact member moves from said assembly towards its initial position, thereby to prevent immediate conductive disengagement of member from assembly and recent-act member to initial position from said trapping and holding compri ng sets 1 terminal members, a r of contacts cooperable to close and a m .in circuit through said line terminals and load terminal members, one of contacts being movable and the other being stationary designed to catch and hold said movable contact, means tending to separate the contacts, means operable to release said movable contact, an a thermostat device disposed in the path of said movable contact and designed to prevent complete separation of the contacts under normal temperature, said device including an electrical heatin unit connected in parallel with the main circuit through the closed contacts.

4. A s: itch as claimed in claim 5, wherein said thermostat device includes a retractible temperature-responsive element positioned adjacent said stationary contact to maintain the movable contact temporarily in engagement with the stationary contact after said movable contact has been released.

5. A thermostatically controlled electric switch comprising a block carrying a stationary contact member and a second contact member movable into engagement therewith from an initial open-circuit position, a bimetallic element disposed substantially perpendicular to the path of said movable member with one end secured to said block and with the other end free and disposed substantially in said path, said contact members being so designed and arranged relaive to the free end of said element that said movable member may readily pass said free end when approaching the stationary member but cannot immediately pass said free end when returning toward initial position, and means for heating said element electrically to cause it to move out of said path after a predetermined interval of engagement with said movable member.

6. A switch as claimed in claim 5, wherein said movable member comprises a spring arm having its ec end twisted about the arm axis, and said stationary member engages said twisted end during return of the spring arm to initial position to force the spring arm into engagement with said bimetallic element.

7. An electric switch of the character described comprising an insulating block for carrylng terminal connections and operating parts, a stationary assembly mounted on one side of said block and including a contact member spaced appreciably from the block, a post secured to the block in offset relation to said assembly and projecting beyond the latter in a direction away from the block, a second contact pivotally supported on said post to swing into and out of engagement with the first mentioned assembly, automatic timing means disposed in the path of said second contact between said stationary contact and the initial position of said second contact, and means for adjusting said second contact axially of said post.

8. An electric switch as claimed in claim 7, wherein said adjusting means comprises a spring urging said second contact outwardly of said post, and threaded means screwed onto the projecting end of the post.

RODERICK A. MACDONALD. 

